Structure-dependent activity of plant natural products against methicillin-resistant Staphylococcus aureus

A Novel Antibiotic, Rhodomyrtone: Pharmacokinetic Studies in a Murine Model and Optimization and Validation of High-Performance Liquid Chromatographic Method for Plasma Analysis

Rhodomyrtone has indisputable and undeniable potential as a new antibiotic for antibiotic-resistant Gram-positive bacteria. Therefore, the main objective of this study was to determine the pharmacokinetics profiles of orally administered rhodomyrtone in rats. A reverse-phase HPLC-UV method was developed, optimized and validated for the analysis of rhodomyrtone concentrations in rat plasma. The retention time of papaverine and rhodomyrtone was 3.928 and 5.937 min, with no interference with the excipients used. The lower limit of quantification (LLOQ) of rhodomyrtone in the plasma sample was 0.04 μg/mL, the accuracy of rhodomyrtone at the LLOQ level ranged from 93.64 to 106.36%, precision was 6.59%, 80-120% for accuracy and <20% CV for precision. The calibration curve was linear at concentrations ranging from 0.04 to 128 µg/mL with a correlation coefficient (r) value of equal to or greater than 0.999. Sprague Dawley rats received a single dose of rhodomyrtone at 50 and 100 mg/kg. Blood samples were collected from tail veins. The peak plasma concentration was observed at 2 h, and the area under the curve of rhodomyrtone at 50 mg/kg and 100 mg/kg was 3.41 ± 1.04 and 7.82 ± 1.53 μg·h/mL, respectively. The results demonstrated linear pharmacokinetics characteristics at the studied dosage range. The plasma concentration of rhodomyrtone was above the minimal inhibition concentrations of several common pathogenic bacteria of medical importance. The proposed HPLC-UV method is fast, cost-effective, reliable and reproducible, and it is proposed for the routine analysis of rhodomyrtone.

Regioselective and Stereoselective Synthesis of Parthenolide Analogs by Acyl Nitroso-Ene Reaction and Their Biological Evaluation against Mycobacterium tuberculosis

Historically, natural products have played a major role in the development of antibiotics. Their complex chemical structures and high polarity give them advantages in the drug discovery process. In the broad range of natural products, sesquiterpene lactones are interesting compounds because of their diverse biological activities, their high-polarity, and sp3-carbon-rich chemical structures. Parthenolide (PTL) is a natural compound isolated from Tanacetum parthenium, of the family of germacranolide-type sesquiterpene lactones. In recent years, parthenolide has been studied for its anti-inflammatory, antimigraine, and anticancer properties. Recently, PTL has shown antibacterial activities, especially against Gram-positive bacteria. However, few studies are available on the potential antitubercular activities of parthenolide and its analogs. It has been demonstrated that parthenolide's biological effects are linked to the reactivity of α-exo-methylene-γ-butyrolactone, which reacts with cysteine in targeted proteins via a Michael addition. In this work, we describe the ene reaction of acylnitroso intermediates with parthenolide leading to the regioselective and stereoselective synthesis of new derivatives and their biological evaluation. The addition of hydroxycarbamates and hydroxyureas led to original analogs with higher polarity and solubility than parthenolide. Through this synthetic route, the Michael acceptor motif was preserved and is thus believed to be involved in the selective activity against Mycobacterium tuberculosis.